[unreadable] The overall goal of this project is to design and build cameras that can efficiently detect and image isotopes that have gamma rays with energies that are typically beyond those effectively accessible with conventional cameras. There are no nuclear medicine clinical cameras, today, that combine high efficiency with the ability to image high-energy gamma rays. The availability of a camera that can image energies in the 0.3 - 3 MeV range would provide higher resolution and earlier detection of tumors than currently available in PET procedures. Such a camera would also assist researchers to develop and use therapies with isotopes that are currently not capable of being imaged. An example is NIH/NCI sponsored extramural and intramural research for both metastatic melanoma and intra peritoneal disseminated disease treatments using targeted Pb-212 and Bi-212 radiotherapy. Both of these projects obtained promising preclinical results and are expected to proceed to clinical trials. The camera being proposed would be suitable to image the therapeutic dose and would therefore be helpful in ascertaining tumor uptake, and subsequent turnover. In addition to directly benefiting 212 based therapy, this camera would open new applications to other isotopes that heretofore are not capable of being imaged. To meet this need we propose to design a system for efficient (high sensitivity) in vivo imaging of the distribution (200-400 micron resolution) of an isotope emitting a high-energy gamma ray. Only Compton Coincidence imaging (CCI) devices could meet this requirement. The detection system will be designed using GEANT 4.5 simulation tools that are operational on the Vanderbilt University Linux Cluster (ACCRE system) using methods developed in our previous research with CCI imaging systems. For this Phase I STTR we will design a camera and demonstrate its performance via computer modeling. After successfully completing this Phase I grant and meeting the minimal objective performance targets we have set, a Phase II proposal will be submitted to assemble the camera and test its performance for a range of energies and applications. [unreadable] [unreadable]